<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>圆角边框</title>
  <style>
    .box {
        width: 200px;
        height: 200px;
        margin: 0 auto;
        border: 1px solid;
        /* 左上水平半径，右上水平半径，右下水平半径，左下水平半径 / 左上垂直半径，右上垂直半径，右下垂直半径，左下垂直半径 */
        border-radius: 10px 20px 30px 40px / 10px 20px 30px 40px;
        /*border-radius: 10px 20px 30px 40px;*/
        /*border-radius: 10px 20px;*/
        /*border-radius: 10px;*/
    }
    img {
        height: 300px;
        display: block;
        margin: 0 auto;
    }
  </style>
</head>
<body>
  <div class="box"></div>
  <img src="./images/border-radius原理.png" alt="border-radius原理">
</body>
</html>
